Retirement and Other Benefit Plans - Schedule Of Reconciliation Of Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Retirement and Other Benefit Plans
Net benefit obligation at beginning of year	$ 89,800	$ 95,300
Interest cost	3,700	3,400	$ 3,200
Actuarial loss (gain)	11,300	(4,300)
Gross benefits paid	(4,700)	(4,600)
Settlements	0	0
Net benefit obligation at end of year	$ 100,100	$ 89,800	$ 95,300